Have you ever been stung by a fire ant? Even if you haven’t, you probably know how (supposedly) bad and evil fire ants are. Yet fire ants, and a couple other well-known invasive ant species like Argentine ants, are only a few out of about 13,000 known species of ants, and they give all of these other species a bad rap. So today, let’s look at a new study by co-first authors Kevin Li and Yifan He and colleagues that properly flips the script: invasive plants push around friendly native ants.

The big bad shrub, Elaeagnus umbellata

As regular readers of The Daily Ant know already, ants harbor lots of bacteria. A growing number of studies are revealing that we should investigate these microbial communities, and their associations with their hosts, in order to fully understand the ecology and evolution of ants. In pursuit of this goal, Manuela Ramalho and colleagues just published an interesting study on the microbial composition of one of the coolest ant groups – Polyrhachis, the spiny ants.

Polyrhachis ant, with its microbial community. Photo: Melvyn Yeo

Every living thing needs nutrients. Much previous work has shown that a variety of soil nutrients – in particular Nitrogen (N), Phosphorous (P), and Potassium (K) – greatly impact plant communities. Often, human behaviors, especially agricultural practices like fertilization, have generated significant shifts in these nutrients. When environments become flushed with these nutrients, overall biomass typically increases but biodiversity often decreases. This is expected according to two hypotheses:

  1. Nutrient Limitation Hypothesis: Limitations in nutrients suppress abundance, and therefore increases in nutrients will drive increased abundance.
  2. Community Homogenization Hypothesis: Species that are most efficient at utilizing resources are prevented from completely excluding other species due to resource limitations. Therefore, increases in nutrients will allow these species to competitively exclude other species, decreasing overall diversity.